✅ Install KiCad
✅ Python & wxPython knowledge

⦿ Create a blank project ▷ Open "PCB Editor" ▷ Click "Show the Python scripting console".

⦿ Enter the following command at "2".

>>> import wx ↩️
>>> wx.MessageBox("Hello World") ↩️

⦿ Create a Hello_World.py file.
⦿ Enter the following code.

import pcbnew
import os
import wx

class SimplePlugin(pcbnew.ActionPlugin):
    def defaults(self):
        self.name = "Hello World"
        self.category = "A descriptive category name"
        self.description = "A description of the plugin and what it does"
        self.show_toolbar_button = False # Optional, defaults to False
       
    def Run(self):
        # The entry function of the plugin that is executed on user action
        wx.MessageBox("Hello World")

SimplePlugin().register() # Instantiate and register to Pcbnew

⦿ put it in:
    Windows: ...\Documents\KiCad\6.0\scripting\plugins\
    MacOS: .../Documents/KiCad/6.0/scripting/plugins/
⦿ Open PCB Editor ▷ Tools ▷ External Plugins ▷ Hello World

Show "Hello World" OK ↩️

PCBNEW